Conventionally, there have been some proposals of oral compositions for removing tooth stain.
For example, the pamphlet of International Publication WO 2007/145287 (Patent Document 1) discloses an oral stain remover containing ultraphosphate. The pH of this oral stain remover is 5 to 6.5 (see paragraph [0024] and [0033] of the document).
Japanese Unexamined Patent Publication No. 2009-126819 (Patent Document 2) discloses a dental whitening agent containing hydrogen peroxide or carbamide peroxide as a radical promoter.
Japanese Unexamined Patent Publication No. 2009-024009 (Patent Document 3) discloses a chewing gum composition for removing stain from dental surface, which includes peroxides and polyphosphates.
Japanese Unexamined Patent Publication (Translation of PCT Application) No. 2006-504776 (Patent Document 4) discloses a composition for removing stain from tooth surface, which includes peroxides and polyphosphates.
Japanese Unexamined Patent Publication No. 2009-51734 (Patent Document 5) discloses a liquid composition for oral cavity containing a salt of polyphosphates, acyl taurine salt and polyethylene glycol, the average molecular weight of which is 600, and having pH 7 to 9.